Field of the Invention
The present invention relates to a bearing lubricating structure for a gas turbine engine, the engine including a low-pressure system shaft, and a high-pressure system shaft fitted to an outer periphery of the low-pressure system shaft in a relatively rotatable manner, in which the low-pressure system shaft is supported by a casing via a first bearing, the high-pressure system shaft is supported by the low-pressure system shaft via a second bearing, and oil is supplied to the first bearing and the second bearing from an oil supply source.
Description of the Related Art
A twin-spool gas turbine engine, in which a high-pressure system shaft is disposed on an outer periphery of a low-pressure system shaft in a relatively rotatable manner, includes: a bearing with which the low-pressure system shaft and the high-pressure system shaft are supported by a casing; and a differential bearing disposed between the low-pressure system shaft and the high-pressure system shaft. The low-pressure system shaft and the high-pressure system shaft are designed to rotate reversely to each other for the purpose of enhancing aerodynamic performances of a compressor and a turbine. Thus, relative rotation speed between an inner race and an outer race becomes large in the differential bearing disposed between the low-pressure system shaft and the high-pressure system shaft so that an amount of oil needed to lubricate the differential bearing increases. Against this background, Japanese Patent Application Laid-open No. 10-299416 has made publicly known a gas turbine engine in which oil injected from an oil jet is supplied to the differential bearing via oil passages, oil reservoirs and oil holes.
However, the foregoing conventional gas turbine engine is likely to be unable to supply a sufficient amount of oil to the differential bearing which needs a larger amount of oil because the bearing with which the low-pressure system shaft is supported by the casing is disposed in a supply passage of the oil from the oil jet to the differential bearing so that the bearing consumes the oil. Supplying of the sufficient amount of oil to the differential bearing may be achieved by increasing capacity of an oil pump. However, the increase in the capacity of the oil pump raises a problem of: making an oil tank and the oil pump bulky in size; and accordingly increasing weight and cost of the gas turbine engine.